Abstract: A system and a method topically applies nitric oxide to an infected area of tissue to treat a wound or lesion to prevent infection, reduce pathogen levels in the infected area and promote healing. The basic system includes a source of nitric oxide gas and a flushing envelope. The flushing envelope is applied to an animal to cover a wound and receives nitric oxide from the source via a flow control valve. One form of the system includes a vacuum unit fluidically connected to the flushing envelope, and one embodiment includes a gas absorber unit. The flushing envelope is adapted to surround the area of the infected tissue and form a substantially air-tight seal with the tissue surface when the flushing envelope is in place on the animal. The flow control valve controls the amount and concentration of nitric oxide gas that is delivered to the flushing envelope.